1. Field of the Invention
The present invention relates to an image processing apparatus processing color image data including two or more types of image data and, more specifically, to a technique of outputting color image data including two or more types of image data in good color tone.
2. Description of the Background Art
Recently, a display apparatus including a large display and a PC (Personal Computer) connected thereto comes to be widely used as a presentation tool for a meeting, conference and the like. PC displays data and the like input from an external device such as a scanner on the large display. The large display gives highly effective visual impression to the attendants of a conference and improves information transmitting effect of the presentation.
As a method of more effectively using a display apparatus as such, the display apparatus may be connected to an image forming apparatus to form a system. If it becomes possible to print the data displayed on the display apparatus, the printout may be used as materials or proceedings of the conference. The systemization attains the effects of better understanding of conference contents by the attendants and better knowledge of conference contents by parties involved but not attending the conference.
In a meeting, a user of the display apparatus may display data read from a scanner (hereinafter referred to as “read data”) on the large display and he/she may write electronic figure, character data and the like using a drawing application, for example, to indicate a part of the displayed image or to write notes. Data written in this manner will be hereinafter referred to as “written data.” When combined data including the read data and written data is displayed on a screen, the written data tends to appear brighter and sharper than the read data. The reason may be that the user often selects a brilliant color different from the read data on the background, when he/she forms the written data. Thus, on the displayed image, the written data and read data are displayed distinguished from each other and, therefore, the written data can serve as a pointer.
When image data provided by combining different types of data is to be output to a certain device, sometimes there arises a problem in the image to be output.
By way of example, broadcast image handling image signals of a plurality of different formats (hereinafter referred to as “multi-format data image”) sometimes encounters the following problem. The multi-format data image refers to an image on which image signals of different formats such as moving image, still image and teletext broadcasting are displayed on one image plane. The moving image, still image and teletext broadcasting have mutually different image characteristics and, when an image of a certain type is to be displayed with high quality, image or images of other type or types come to be less visible.
A solution to such a problem is disclosed in Japanese Patent Laying-Open No. 2002-44559 (hereinafter referred to as “'559 application”). According to the technique disclosed in '559 application, in multi-format broadcast image, data of various formats are separated from each other to form layered image signals, different image processing is executed on each layered image signal in accordance with parameters set in advance in accordance with characteristics of each data, and thereafter, the results are combined and displayed. Therefore, it is possible to improve image quality in displaying data of each format.
In the image processing apparatus displaying combined data in which read data and written data are superposed, when the combined data is printed, particularly the written data tends to be less sharp or darker and duller than when it is displayed. This is because RGB value ranges that the read data can assume on the display differ from those of the written data.
Graph 1 shown in FIG. 1A represents the ranges of RGB values for the read data. Graph 2 shown in FIG. 1B represents the ranges of RGB values for the written data. In FIGS. 1A and 1B, the abscissa represents the value of R, the depth represents the value of G and the ordinate represents the value of B, respectively. Numerical ranges of R, G and B values are each 0.0 to 255.0.
Referring to FIGS. 1A and 1B, when we compare Graph 1 (read data) with Graph 2 (written data), it can be seen that read data has narrower numerical ranges of R, G and B values than the written data. This comes from characteristics of an image reading device such as a scanner. When images having RGB value ranges different from each other are simply superposed and processed for printing, it is impossible to print images all in a preferred manner.
The apparatus disclosed in '559 application is directed to improving display image quality when image signals of mutually different formats are displayed superposed one after another. Therefore, this technique cannot directly be applied when image data having different RGB value ranges are to be combined and printed. Accordingly, the technique disclosed in '559 application cannot solve the problem that combined data including read data and written data cannot appropriately be printed by the image processing apparatus.
There is also a problem peculiar to the written data that the data is visibly well recognized when displayed in brilliant color on the screen while the written data is printed not in such a brilliant color but dull tone and hence, it becomes difficult to distinguish the written data from the read data. The technique disclosed in '559 application cannot solve such a problem, either.
Specifically, the conventional technique has a problem that appropriate image processing cannot be done on image data including color image data of a first type and color image data of a second type.